Water-absorbing (meth) acrylic resin with optical effects, and related compositions

ABSTRACT

A water-absorbing polymer obtained from (A) a phosphate-containing (meth)acrylic monomer and/or a salt thereof, (B) a monomer having one (meth)acrylic group within the molecule and/or a salt thereof other than component (A), and (C) an organopolysiloxane having a (meth)acrylic group at both ends and related compositions.

TECHNICAL FIELD

This invention relates to a water-absorbing (meth)acrylic resin, and askin external preparation comprising the same suitable as cosmetics.

BACKGROUND ART

In the field of skin external preparations including cosmetics and skinexternal drugs, water-absorbing polymers are used in aqueous cosmeticsand aqueous skin external drugs as a thickening/gelling agent forstabilizing the system. The water-absorbing polymers, however, have thedrawback that they give an unpleasant slimy feel on use. This is becausethe polymer forms a gel network structure, which is stable and thusdifficult to break down on use. Because of the unpleasant feel,sometimes the use of the cosmetic or drug must be interrupted. While itis desired to solve the problem, non-silicone water-absorbing polymersare unsatisfactory. See Patent Document 1.

To solve the drawback of an aqueous skin external preparation using awater-absorbing polymer, Patent Documents 2 and 3 proposewater-absorbing polymers having a silicone structure incorporatedtherein and cosmetic compositions comprising the same. Thesewater-absorbing polymers still have problems including difficult controlof three-dimensional structure due to cross linking of epoxy groups, anda change with time of water absorption capability.

Thus, it is desirable to create water absorbing polymers that provideoptimal aesthetics as well as to provide other desirable cosmeticproperties. If an ingredient used to formulate cosmetic products canmultiple functions, this means fewer ingredients can be used in theformulation which reduces cost and the potential for adverseinteractions between ingredients.

Particularly in cosmetic applications, it is very desirable to create afilm on skin that blurs skin defects such as lines, wrinkles, or minorskin imperfections. In addition to provide aesthetically pleasingthickening properties, when the same polymers provide other benefitssuch as optically improving the appearance of the skin surface thisprovides a further advantage.

CITATION LIST

Patent Document 1: JP-A 2000-327516

Patent Document 2: WO 2007/130412

Patent Document 3: WO 2007/130460

SUMMARY OF INVENTION

An object of the invention is to provide a cosmetic composition whichexerts a high thickening effect in aqueous solvents, eliminates poorspreading, moist and sticky feels, and is in paste form havingthixotropy and giving a dry light feel.

Another object of the invention is to provide a cosmetic compositioncontaining such polymer, which also provides optical effects on skinsuch as blurring the appearance of skin imperfections and providing thevisual appearance of smooth, homogeneously colored skin.

The inventors have found that using a water-absorbing polymer definedherein, a skin external composition is formulated that can attain theabove objectives and other objects.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows photographs taken at two minutes of glass slides onto whichthe invention and comparative compositions were applied according to theprocedure in Example 2.

FIG. 2 shows photographs taken at 2 hours of glass slides onto which theinvention and comparative compositions were applied according to theprocedure in Example 2.

DESCRIPTION OF PREFERRED EMBODIMENTS

Component (A) is a phosphate-containing (meth)acrylic monomer. As longas a monomer has a phosphate group and a (meth)acrylic group, thestructure of a linkage for connecting these two groups is notparticularly limited. Exemplary linkages include alkylene groups such asmethylene, ethylene and propylene and oxyalkylene groups such asoxyethylene, oxypropylene, oxybutylene, oxypentamethylene and mixturesthereof. Of these, polyoxyalkylene groups are preferred, withpolyoxypropylene being most preferred. The monomer is commerciallyavailable, for example, under the tradename of Sipomer PAM-200 fromRhodia.

Also included is a salt of a phosphate-containing (meth)acrylic monomer,which may be formed by adding an alkaline aqueous solution to thephosphate-containing (meth)acrylic monomer.

Component (B) is a monomer having one (meth)acrylic group within themolecule other than component (A). Suitable (meth)acrylic monomersinclude (meth)acrylic acid, maleic acid, maleic anhydride, fumaric acid,crotonic acid, itaconic acid, 2-(meth)acrylamide-2-methylpropanesulfonicacid, (meth)acryloxyalkanesulfonic acid, N-vinyl-2-pyrrolidone,N-vinylacetamide, (meth)acrylamide, N-isopropyl(meth)acrylate,N,N-dimethyl(meth)acrylamide, 2-hydroxyethyl(meth)acrylate,methoxypolyethylene glycol (meth)acrylate, polyethylene glycol(meth)acrylate, and strearyl acrylate. A salt of the (meth)acrylicmonomer may be formed by adding an alkaline aqueous solution to the(meth)acrylic monomer.

The “salt” includes alkali metal salts such as sodium, potassium andlithium, alkaline earth metal salts such as calcium, magnesium andbarium, and ammonium salts such as quaternary ammonium and quaternaryalkyl ammonium. Inter alia, sodium salt is the most common andpreferred. Neutralization treatment is preferably carried out at atemperature of 10 to 100° C., more preferably 20 to 90° C. Acrylic acidor polyacrylic acid following polymerization may be neutralized with abase. Neutralization prior to polymerization is preferred because it istime consuming to post-neutralize non-neutralized or low-neutralized(specifically a degree of neutralization of less than 30 mol %)polyacrylic acid following polymerization. The water-absorbing polymerof the invention preferably has a degree of neutralization of 0.01 to100%, more preferably 1 to 90%, and even more preferably 20 to 80% basedon the moles of acid groups in the polymer.

Component (C) is an organopolysiloxane having a (meth)acrylic group atboth ends, represented by the general formula (1).

Herein R¹ is each independently an aliphatic unsaturation-freemonovalent hydrocarbon group having 1 to 8 carbon atoms. R² is a groupcontaining a polyoxyalkylene group having the general formula (2):—R⁴(OC₂H₄)x(OC₃H₆)yOH  (2)wherein R⁴ is each independently a divalent organic group having 2 to 15carbon atoms, x and y each are an integer of 0 to 30, meeting 1≦x+y≦50.R³ is a substituent group having a (meth)acrylic group, a is an integerinclusive of 0 and b is an integer of at least 1.

Examples of the monovalent hydrocarbon group represented by R¹ includealkyl groups such as methyl, ethyl and butyl, cycloalkyl groups such ascyclopentyl and cyclohexyl, aryl groups such as phenyl and tolyl, andaralkyl groups such as benzyl and phenethyl. Inter alia, alkyl groups of1 to 4 carbon atoms and phenyl are preferred, with methyl being mostpreferred.

In formula (2), R⁴ is each independently selected from divalent organicgroups having 2 to 15 carbon atoms, for example, —(CH₂)₂—, —(CH₂)₃—,—(CH₂)₄—, —CH₂CH(CH₃)CH₂—, —(CH₂)₈—, and —(CH₂)₁₁—. Inter alia,—(CH₂)₂—, —(CH₂)₃—, and —(CH₂)₄— are preferred. Each of x and y is aninteger of 0 to 30, meeting 1≦x+y≦50. Preferably each of x and y is aninteger of 5 to 25, more preferably 10 to 20, and the sum of x+y is 10to 45, more preferably 20 to 40.

In the water-absorbing polymer, the phosphate-containing (meth)acrylicmonomer and/or salt (A) is preferably present in a content of 30 to 95%by weight. A polymer containing less than 30% by weight of monomer (A)may be less water absorptive whereas a polymer containing more than 95%by weight of monomer (A) may not become pasty after water absorption.The content of monomer (A) is more preferably 40 to 95% by weight, andeven more preferably 50 to 80% by weight. Also preferably, the(meth)acrylic monomer and/or salt (B) is present in a content of 4 to50% by weight, more preferably 15 to 50% by weight, and theorganopolysiloxane (C) is present in a content of 0.01 to 20% by weight,more preferably 2 to 20% by weight.

The water-absorbing polymer may be prepared typically by radicalpolymerization reaction. Although the procedure is not particularlylimited, the polymer may be prepared, for example, by diluting monomers(A) and (B) with a solvent, optionally adding an alkali, andpolymerizing the monomers with siloxane (C) in the presence of (D) aradical initiator.

The radical polymerization mode for preparing the water-absorbingpolymer is not particularly limited. While bulk polymerization andprecipitation polymerization are acceptable, reverse phase suspensionpolymerization, spray or dropwise polymerization, and aqueouspolymerization, especially continuous aqueous polymerization arepreferred for polymer performance and ease of polymerization control.

A dispersant may be used during polymerization. Suitable dispersantsinclude cationic and ampholytic surfactants such as sorbitan fatty acidesters and carboxymethyldimethylcetyl ammonium, anionic surfactants suchas sodium salt of polyoxyethylene dodecyl ether hydrogensulfate, andpolymeric dispersants such as cellulose esters, maleic polybutadiene,and quaternary salt of isopropyl methacrylate-dimethylaminoethylmethacrylate. These dispersants may be used alone or in admixture of twoor more. The amount of the dispersant used is preferably 0.01 to 5 partsby weight per 100 parts by weight of the monomer charge. In the case ofreverse phase suspension polymerization, an ionic surfactant ispreferably used to disperse the monomers because it is also effectivefor preventing agglomeration of highly water-absorbing resin particles.

The polymerization initiator which can be used in the synthesis of thewater-absorbing polymer may be selected depending on the polymerizationmode. Examples of the polymerization initiator includephoto-decomposable initiators, thermally decomposable initiators, andredox initiators. The amount of the polymerization initiator used istypically 0.001 to 10 mol %, preferably 0.001 to 5 mol % based on themonomer charge. Outside the range, an excess of the initiator may causecoloring or an offensive odor whereas a less amount may lead to anincreased amount of residual monomers.

Examples of the photo-decomposable polymerization initiators includebenzoin derivatives, benzyl derivatives, acetophenone derivatives,benzophenone derivatives and azo compounds. Examples of the thermallydecomposable polymerization initiators include persulfates such assodium persulfate, potassium persulfate, and ammonium persulfate,peroxides such as hydrogen peroxide, t-butyl peroxide, and methyl ethylketone peroxide, azo compounds such as2,2′-azobis(2-amidinopropane)dihydrochloride and2,2′-azobis[2-(2-imidazolin-2-yl)propane)dihydrochloride, andperchlorates such as potassium perchlorate and sodium perchlorate.Examples of the redox polymerization initiators include combinations ofthe above persulfates or peroxides with reducing compounds such assulfites, L-ascorbic acid or ferrous salts. It is also possible to usethe photo-decomposable initiator and thermally decomposable initiator incombination. Among others, the peroxides are preferred for attaining theobjects of the invention.

The polymerization initiator may be added all at once or dropwise in theform of a solution. Divided portions of the initiator may be added inthe course of reaction.

The polymerization results in a water-absorbing polymer in hydrous gelform, from which the desired water-absorbing resin may be recoveredthrough post-treatment as desired, for example, washing for the purposeof removing any residual monomers and the initiator and drying. For thewashing step, any solvent such as water, acetone, alcohols, isoparaffinor volatile silicone may be used, although the solvent is notparticularly limited. The solvents may be used alone or in combination,or stepwise for carrying out washing.

The drying step is not particularly limited as long as it isconventional. The preferred modes of drying include heat drying, hot airdrying, vacuum drying, IR drying, microwave drying, freeze drying, spraydrying, azeotropic drying using hydrophobic organic solvent, andhigh-humidity drying using hot steam. Hot air drying is more preferred.Although the drying temperature and time are not particularly limited,drying at a high temperature above 150° C. or for a long time of morethan 5 hours may give rise to such problems as alternation of the resin,a drop of water absorption factor, and coloring.

If desired, the drying step may be followed by adjustment of particlesize or narrowing of particle size distribution via surfacecrosslinking. The particle size may be adjusted via polymerization,grinding, classification, granulation or fines recovery.

For the surface crosslinking, a surface crosslinking agent is used.Various organic and inorganic surface crosslinking agents are known,with the organic crosslinking agents being preferred. Suitablecrosslinking agents are dehydration esterification crosslinkersincluding polyhydric alcohols, epoxy compounds, polyfunctional aminecompounds or condensates thereof with halo-epoxy compounds, oxazolinecompounds, and (mono, di or poly)oxazolidinone compounds.

The silicone-crosslinked water-absorbing polymer may take any shapeincluding spherical, mass, flake, plate, oval, fiber, irregular, acompact of consolidated particles and other shapes.

The silicone-crosslinked water-absorbing polymer preferably has anaverage particle size of 100 nm to 1 mm, more preferably 500 nm to 500μm, in a state prior to water absorption (i.e., a loss of up to 5% on150° C./3 hour heating) although the average particle size is notcritical.

The silicone-crosslinked water-absorbing polymer functions to convertwater solvent into gel. The term “gel” means that the water-absorbingpolymer absorbs a low-viscosity liquid so that the liquid may exhibit noor substantially no fluidity. The water solvent may be water alone or amixture of water and an organic solvent. The organic solvent which ismixed with water is not particularly limited. Among others, amphiphaticsolvents are preferred, for example, alcohols such as methanol, ethanol,propanol and 2-propanol, ketones such as acetone, and ethers such astetrahydrofuran and dioxane.

Another embodiment of the invention is a cosmetic or skin externalpreparation comprising 0.01 to 60%, preferably from about 0.1 to 20%,more preferably from about 0.1 to 10% by weight (based on the totalweight of the preparation) of the water-absorbing polymer defined above.

As used herein, the “skin external preparation” refers to anypreparations externally administered to the skin, for example,cosmetics, skin external drugs, skin external disinfectants andbactericides. The term “cosmetic composition” means a composition thatis applied to keratin surfaces for purposes of treatment,beautification, or coloration. Better results are obtained when theinvention is applied to cosmetics where the feel on use has a largeimpact on the effect and skin external drugs requiring long-termcontinuous administration, and especially cosmetics.

The preparation or composition may take the form of lotion, gel,emulsion, cream, powder dispersion, powder dispersion emulsion, or thelike. If the composition is in emulsion form, the emulsion may bewater-in-oil or oil-in-water. In such case, the composition may comprisefrom about 2-99% water and from about 1-98% oil.

Various types of cosmetic composition are included, for example, skincare products, foundation make-up cosmetics, and hair care cosmetics.

EXAMPLE

Examples are given below to illustrate the synthesis of water-absorbingpolymers and cosmetic compositions using them, but the invention is notlimited thereto.

Synthesis Example 1

A 1-L separable flask equipped with a stirrer was charged with 24 g ofmethacrylic acid, 60 g of Sipomer PMA-200 (Rhodia), and 100 g ofdeionized water. With stirring, 52 g of 25% sodium hydroxide aqueoussolution was added dropwise at 20-30° C. To the solution, 12 g of amethacrylic-terminated siloxane having the following formula (3) wasadded. With stirring, nitrogen bubbling was continued for 30 minutes,whereupon 100 g of 4% potassium peroxydisulfate aqueous solution wasadded at 25° C. Thereafter, the flask was heated at 60° C. at whichreaction was run for 10 hours. The resulting gel was washed with anexcess of acetone/water mixture, filtered, dried in a vacuum dryer for10 hours, and pulverized in a mill, yielding the desired water-absorbingpolymer in white powder particle form.

Synthesis Example 2

A 1-L separable flask equipped with a stirrer was charged with 24 g ofmethacrylic acid, 60 g of Sipomer PMA-200 (Rohdia), and 110 g ofdeionized water. With stirring, 52 g of 25% sodium hydroxide aqueoussolution was added dropwise at 20-30° C. To the solution, 6 g of amethacrylic-terminated siloxane having the formula (3) was added. Withstirring, nitrogen bubbling was continued for 30 minutes, whereupon 50 gof 4% potassium peroxydisulfate aqueous solution and 25 g of 4% sodiumhydrogensulfite aqueous solution were added at 25° C. Thereafter, theflask was heated at 50° C. at which reaction was run for 5 hours. Theresulting gel was washed three times with an excess of acetone/watermixture, filtered, dried in a vacuum dryer for 10 hours, and pulverizedin a mill, yielding the desired water-absorbing polymer in white powderparticle form.

Example: Cosmetic Composition

A cosmetic composition containing the polymer of Example 1 was preparedalong with comparative formulas, as set forth below.

Invention Comparative Comparative Comparative Ingredient Formula Formula#1 Formula #2 Formula #3 Water QS100 QS100 QS100 QS100 Sodium 4.00acrylate crosspolymer- 1¹ Sodium 0.30 Acrylate crosspolymer- 2² Butylene2.0 2.0 2.0 2.0 glycol Sucrose 0.5 0.5 0.5 0.5 Sorbitol 0.35 0.35 0.350.35 Caprylyl 0.20 0.20 0.20 0.20 glycol Glucose 0.05 0.05 0.05 0.05Disodium EDTA 0.05 0.05 0.05 0.05 Laminaria 0.02 0.02 0.02 0.02 digitataextract Sodium 0.75 polyacrylate³ Carbomer⁴ 0.30 Tromethane 0.30Glycerin 15.00 15.00 15.00 15.00 ¹Polymer of Example 1 ²Aqua Keep10SH-NFC - Sodium Acrylate Crosspolymer-2. Kobo Products Inc. ³CosmediaSP - Sodium polyacrylate. Cognis Corporation ⁴Carbopol 980 - Carbomer -Momentive Performance Materials

The amount of the polymers used initially was adjusted so that the finalviscosity of the inventive and comparative formulas was essentially thesame to facilitate comparative evaluation, e.g. ranged from 24,000 to36,000 cps at 25° C.

The compositions were tested for ability to optically improve theappearance of surfaces such as skin. 6 mil of each composition wasapplied to a microscope glass slide using a square applicator. Theslides were dried in an air conditioned room at 25° C. The slides werephotographed by a Canon PowerShot SD1400 IS camera where images weretaken with the slides placed on a black background and the photographtaken at a 45° angle. Photographs were taken at 2 minutes, 2 hours and24 hours. The results are show in FIGS. 1 and 2. The slides to which theinvention composition was applied show an even film that provides ahomogeneous light coverage that when visually inspected appears to blurthe underlying glass slide. This is confirmed by application to skinwith visual observation.

The invention claimed is:
 1. A cosmetic composition comprising sodiumpolyacrylate crosspolymer-1.
 2. The cosmetic composition of claim 1wherein the sodium polyacrylate crosspolymer-1 is present at 0.1 to 60%by weight of the total composition.
 3. The cosmetic composition of claim1 wherein the cosmetic is in the form of an emulsion.
 4. The cosmeticcomposition of claim 3 wherein the emulsion is a water in oil emulsion.5. The cosmetic composition of claim 3 wherein the emulsion is an oil inwater emulsion.
 6. The cosmetic composition of claim 1 which is a skintreatment cream or lotion.
 7. The cosmetic composition of claim 1 whichis a foundation makeup.